The two English radio amateurs were manning their radio telescope, much as they had during every spare waking hour for the past three weeks, in search of an intelligent signal from the stars. As UK Co-Coordinators for Project Argus, the all-sky survey launched by The SETI League on Earth Day, April 21, 1996, their job was to assist other British hams in building sensitive microwave listening posts. Their 3.5 meter diameter dish and associated electronics were put together as a demonstration station, and now they were demonstrating the patience and deliberation for which their one hundred combined years had uniquely prepared them. They were systematically analyzing an anomaly.

Ken's colleague knew that Low Earth Orbit satellites were the bane of SETI, the scientific Search for Extra-Terrestrial Intelligence. Fortunately, their Doppler shift, a change in radio frequency caused by their motion relative to the Earth, made such man-made sources readily distinguishable from signals of interstellar origin. Still, there was something odd about this particular signal.

The Argus concept had been born in the States a year and a half earlier, in response to Congress canceling all of NASA's SETI funding. For just a couple of years, NASA had conducted a modestly funded SETI effort from headquarters at the Ames Research Center in Mountain View, CA. Consuming just one tenth of one percent of NASA's science budget, or about five cents per American per year, NASA SETI promised to be one of the best scientific bargains of all time. Then the budget-balancers axed it, reducing the US national debt in the process -- by point zero zero zero six percent.

A group of American microwave experimenters was not about to let the Search die for lack of intelligence in Washington. Ken and Trevor had heard about their amateur effort at the World Science Fiction Convention in Glasgow the previous summer, and were the first Europeans to sign on. Now their many months of effort and training were being put to the test.

"Save to disk," commanded Trevor unnecessarily, for Ken was already doing so. "Let's get a GIF, and also maybe a WAV file. We're going to have to Internet this one."

It was a moment of great excitement, for this "Wow!" event exhibited many of the characteristics we would expect of an intelligently generated microwave signal from space. Still, restraint was the order of the day. The experimenters sent their signal file to Dr. SETI (that's me.)

The signal looked for all the world to have originated from space, but its Doppler shift (that artifact of relative motion which makes railroad whistles and radio signals alike change in frequency over time) was suggestive of near space. This appeared to be a low Earth orbit satellite which Ken and Trevor had snared. Still, it was a worthy detection, for three reasons:

This was an extremely weak signal, which spoke well for the sensitivity of our participants' homebuilt receiving equipment.

The Doppler shift was instantly evident in the computer printout, which gave us confidence in the capabilities of our signal analysis software.

Most important, our amateur SETIzens did not ring up the Times of London, the BBC, or (heaven forbid!) The Sun (that bastion of journalistic excellence), and proclaim "ET is calling me." Rather, they opted to abide by The SETI League's Signal Verification Protocols, and to Ask Dr. SETI. So we had our first solid evidence that nonprofessionals were indeed capable of shunning sensationalism, and conducting credible science.

Presently, I showed an image of the candidate signal to a room full of radio astronomers at the National Radio Astronomy Observatory in Green Bank, WV, home to the world's first SETI search in 1960. One professional observer exclaimed, "You landed that one on 1470.5 MHz, didn't you?"

"How did you know that?" I asked, stunned.

"Oh, we've seen this baby before. She's a classified US Navy satellite."

Project Argus continues to detect likely candidate signals, and on analysis, all (so far) have had similarly prosaic explanations. But that doesn't lessen our members' excitement at participating in their peculiar brand of electronic archaeology. So far, all of our Argonauts have exhibited the restraint and professionalism which Ken and Trevor modeled for them early on. Still, there have been claims in the media, about once a year, that SETI has indeed detected the evidence we seek. Four times now The SETI League has had to go public with what most would view as disappointing news.

The first false claim we found it necessary to dispel was a simple matter of mistaken identity. The second involved a statement made at a scientific meeting and taken out of context. The third was a matter of a private email cross-posted to the wrong Internet list. These things happen, and are easily rectified. But when the EQ Pegasi Hoax reared its ugly head, even Dr. SETI began to have doubts.

Two and a half years into our search, an anonymous hacker broke into a private signal verification email list, and made claims of an extraordinary nature. He had, he alleged, detected clear, unambiguous evidence of extra-terrestrial intelligence, while using his employer's ten meter satellite dish after hours. He could not identify himself, he claimed, because that would put his job in jeopardy. But here were email attachments, images showing precisely the kinds of signals we were looking for! For three weeks, SETI League members around the world scrambled to test the claim.

Only, it was a total fabrication. The images posted were testimony to the power of our computer technology. However, it was not the capabilities of any signal analysis software which they demonstrated, but rather those of a graphics program called Paint Shop Pro. The images in question were a cut-and-paste masterpiece, all part of an elaborate hoax to discredit SETI.

And it almost worked. When the press ran stories of the powerful signals from the EQ Pegasi binary star system, detected by an amateur radio astronomer, the public ate it up. The SETI community was thrown into damage-control mode. We pointed out that science cannot be done anonymously, that a credible researcher owns his successes as well as his failures. We mentioned that an admitted hacker (he signed his emails 'anon1420') was more likely to plant a virus than to discover aliens. And we emphasized that these powerful, repeating signals from a nearby star system were seen by but one person, day after day, yet somehow eluded detection by dozens of dedicated radio astronomers around the world.

For that claim, we in SETI were labeled part of the Grand Cover-Up. It was suggested in the tabloids that some nefarious Government conspiracy was at work.

So yes; I admit it: I'm part of the Government conspiracy. I pay taxes.

Meanwhile, we continue to search for proof. Which begs the question, what exactly would constitute incontrovertible proof of extra-terrestrial intelligence? That question is complicated by the fact that the general public (from whom the Project Argus constituency is largely drawn) may make only a vague distinction between proof and faith. The spectrum of human skepticism vs. gullibility encompasses a wide range of extremes, characterized by diverse viewpoints ranging from "of course they exist -- we couldn't possibly be alone!" to "I'll believe in the existence of intelligent extra-terrestrials only when one walks up and shakes my hand." We must take pains to prevent such declarations of faith from clouding the judgment of our SETIzens.

We start by acknowledging that one can never conclusively prove the negative, but that it takes only one counter-example to disprove it. Conservative experimental design demands that we frame our research hypothesis in whatís called the null form: "resolved that there are no civilizations in the cosmos which could be recognized by their radio emissions." Now a single, unambiguous signal is all it takes to disprove the null hypothesis, and negate the notion of humankind's uniqueness.

But what exactly constitutes an unambiguous signal? A popular definition holds it to be one which could not have been produced by any naturally occurring mechanism which we know and understand. But this is an insufficient condition. The first pulsars, after all, fitted that definition. They were first labeled "LGM" for Little Green Man, and their intelligent extra-terrestrial origin seriously considered for several months, until our knowledge of the mechanics of rapidly rotating, dense neutron stars became more complete. There is the risk that any signal which cannot be produced by any known natural mechanism could well have been generated by an astrophysical phenomenon which we have yet to discover. So we need an additional yardstick.

We know a priori several of the hallmarks of artificiality which we can expect to be exhibited an electromagnetic emission of intelligent origin. The common denominator of all these characteristics, in fact of all human (and we anticipate, alien) existence, is that they are anti-entropic. Any emission which appears (at least at the outset) to defy entropy is a likely candidate for an intelligently generated artifact. In that regard, periodicity is a necessary, though not a sufficient, condition for artificiality (remembering once again the pulsar).

Ideally, we would hope to receive communication rich in information content, signals which convey otherwise unknown information about the culture which generated them. Unless we are blessed with such a message, we are unlikely to ever achieve absolute certainty that what we have received is indeed the existence proof we seek. Multiple independent observations, however, can do much to dispel the obvious alternative hypotheses of equipment malfunction, statistical anomaly, human made interference, and deliberate hoax. In that respect the development of well coordinated signal verification protocols can do much to narrow our search space. Once again, in signal verification activities, it is the null hypothesis we should be attempting to verify. We thus expect that we will ultimately rule out most candidate signals. There may eventually come a signal, however, which simply cannot be explained away.

"When you have ruled out the impossible," Arthur Conan Doyle wrote in the voice of Sherlock Holmes, "whatever remains, no matter how unlikely, must be the truth." Above all else, this truth must pass the inter-ocular trauma test: when the proof we seek is so powerful as to hit us between the eyes, we can no longer deny it. No Government pronouncement is likely to pass this demanding test, as far as a skeptical public is concerned. But if a diverse, international group of laymen, working independently, can produce multiple, internally consistent observations backed by the corroboration of their professional counterparts, then the world is most likely to accept that group's interpretation as reasonable. SETI continues to seek clear, unambiguous evidence, without even knowing for certain what form that evidence will take. We hope to stumble across the inescapable.

Until we do, we continue to test the null hypothesis.

About The Author

An Extra-class radio amateur first licensed in 1961, N6TX has been operational in all 20 ham bands between 1.8 MHz and 24 GHz. Paul has chaired the VHF/UHF Advisory Committee of the American Radio Relay League, been a Director of the Central States VHF Society and served as Technical Director and Board Chairman of Project OSCAR, Inc. A retired engineering professor, Paul now serves as Executive Director of the nonprofit SETI League, Inc.

Paulís honors include the National Space Club's Robert H. Goddard Scholarship, the American Radio Relay League Technical Achievement Award, a Hertz Foundation Fellowship in the Applied Physical Sciences, the Hertz Doctoral Thesis Prize, and the Central States VHF Society's John T. Chambers Memorial Award. He is a Fellow of the British Interplanetary Society, an FAA Aviation Safety Advisor, serves as a fellowship interviewer for the Hertz Foundation, a manuscript reviewer for several peer reviewed journals, has been an advisor to the National Science Foundation, and is a military program evaluator for the American Council on Education. Paul was Banquet Speaker for several past AMSAT meetings, as well as the 1996 Dayton Hamvention.